Originally Posted by robwod

Check to make sure you are not being "attacked" on your xmlrpc.php file or on your wp-login.php file.

There's a pile of bots hammering those these days and numerous simultaneous xmlrpc.php calls in particular can really drive up your server load if left unchecked. you can try deleting xmlrpc.php if you don't use it. Or add a root based htaccess file to restrict access to the file.